Expulsion fuse



Aug. 16, 1932. c, H. THOMAS EXPLUSION FUSE Filed Jan. 1s, 1929 2 Sheets-Sheet l C. H.A THOMAS EXPLUSION FUSE Aug. 416, 1932.

Filed Jan, 18, 1929 2 Sheets-Sheet 2 l l 1 l/1/ /ll//l/l J m a@ m w ig?,

charred,

Patented Aug. 16, 1932 UNITED STATES CYRIL H. THOMAS, OF FLOSSMOOR, ILLINOIS EXPULSION FUSE Application led January 18, 1929. Serial No. 333,315.

My invention relates in general to electric fuses and has more particular 'reference to fuses of the so-called expulsion type adapted for use in high tension electric circuits.

p It is well known that required to carry appreciable load currents, up to the overload limit at which they are calibrated to operate, for long periods and until the overload occurs, and an important object of my present invention is to provide a fuse of simple, rugged construction permitting production at low cost and having improved operating characteristics whereby the fuse may maintain its high rupturing capactiy and positive opera-tion overlong periods and although subjected to overload and overheating which deteriorate fuses of ordinary construction.

Although fuses for use in high tension switch gear Yare not usually intended for the carrying of overload currents, it frequently happens, under the eXigencies of service, that high tension fuses are subjected to prolonged overload which, althoughcnot suiiicient to blow the fuse, is heavy enough to heat the fuse to a high temperature. Fuses of this general character for use in high tension switch gear are ordinarily formed of aluminum, either pure or alloyed with other metals, and copper and zinc alloys. Such materials can be heated to around 1100 degrees centigrade (barely visible red heat) without fusing. It has heretofore been the custom to provide a housing for high tension fuses consisting of a tube formed of fibrous material impregnated with bakelite, that is to say, a phenolic condensation or reaction product. Tubes of horn fibre, which consist of linen rags treated with zinc sulphite, have also been utilized for this purpose. Bakelite and horn libre char at temperatures in excess of 400 degrees centigrade and consequently when fuse housings formed of these materials are used in high tension switch gear wherein overloads occur, the housings frequently become charred because the fuse operates over long periods at temperatures ranging between 500and 1100 degrees centigrade. It is obvi-V ous, of course, that when the housing is it loses its mechanical strength, its

fuses of this type areinsulating properties, and renders the fuse unfit for further service, and it is an important object of my present invention to provide a fuse embodying a fuse housing of a true non-carbonizing material whereby the fuse 455 may operate for long periods and under overload Vconditions without impairing the Voperating characteristics and ren-dering the same unlit for further service.

A further important object is to provide 6o a fuse support wherein the fuse element is enclosed in an insulating liner having a fire resisting lining of novel and improved construction, which lining will not deteriorate when and if the device is made to carry overload currents for Vappreciable periods, and which resists breakage through rough handling in use or through careless assembling during manufacture.

Heretofore the use of refractory materials as fuse housings in high tension fuse assemblies has been avoided because such materials are fragile to a degree such thatv continuous tubes of such material can not easily be assembled in position, and, when assembled, are readily broken unless the assembly is care'- fully handled, the expense of such careful handling as is necessary being prohibitive for practical purposes. It is therefore an important object of my present invention to provide a rugged and practical fuse assembly wherein an elongated fuse housing of refractory material is provided whereby the advantages of a refractory fuse housing may be had while obviating the disadvantage 0f the Si fragility of the material.

A still further object is to provide a fuse so constructed that the fuse element can be quickly and easily replaced after rupture without special tools, or in fact any tools and arranged for insertion betweenl standard fuse supports.

Numerousother objects and advantages of the invention will be apparent as it is more fully understood from the following description which, taken in connection with the following drawings, discloses a preferred embodiment of the invention.

Referringto the drawings: Y

Y an insulating Figure 1 is a perspective view oi a fuse assembly embodying my invention;

Figure 2 is a perspective assembly view of the elements of the 'fuse illustrated in Figure 1; y

Figure 3 is a vertical cross section taken substantially along line 3-3 in Figure 1;

Figure 4 is a horizontal cross section taken substantially along the line 4-4 in Figure 3; and

Figure 5 is a cross section illustrating a modified construction ot certain oit the parts shown in Figure 3.

To illustrate my invention, l have shown on the drawings a fuse assembly arranged in operative position between Vthe cooperating blades of spaced` useholding clips 11.

The fuse assembly comprises a fuse, a fuse support and a liner for the fuse support. The fuse support comprises a pair ot i'errules or caps 15, 15 supported at the opposed ends oit tube 13, which may be conveniently formed or relatively heavy insulating material, preferably glass, the caps 15 being rovided with sockets Q1 into which the ends of the tube 13 are iitted, the ends of the tube being secured in place in the socketsy 21 by means of bushings or other suitable packing 19. The caps 15, 15 are preferably cylindricall and are adapted to engage between the cooperating blades 11 ot spaced fuse-holding clips, the sides of t ie caps being flattened to provide parallel bearing surfaces on opposite sides thereof whereby the blades 11 ot the 'fuse supporting clips may readily engage and grip the caps to lirmly support the tuse support iny position. Means is provided for securing the opposed ends of a fuse wire 59 to the upper and lower caps 15, 15', the fuse wire extending between the caps through the tube. 13. The upper cap 15 also is provided with an explosion Chamber 37 and the wire 69 is arranged to fuse under load substantially opposite the explosion chamber whereby the force of the arc causedV by the rupturing of the. fuse wire may be directed downwardly through the tube 13 to blow the lower portions ot the fuse wire out ot the holder in order to quickly extinguish the arc formed when the fuse wire ruptures and thus to break the circuit in which the use is placed. Tn order to protect the lower portions of the fuse holder, that is to say the portions below the explosion chamber 37, provide a heat and lire resisting liner of novel construction within the tube ,13 and through which the fuse passes. This liner is supported trom the upper cap 15 and provides a channel leading from the explosion chamber 37 downwardly through the fuse holder to a point substantially below the lower cap 15', through which channel the arc and the hot gases may pass inV expelling the 'use and extinguishing the arc. The lower cap 15` is provided with an outwardly extending boss 23 in its Jforward side provided with a central threaded socket extending axially of the boss and carrying a threaded stud 25, one end of which extends forwardly of the boss and carries a thumb screw 27 whereby the lower end of the fuse wire 69 may be connected to the lower cap 15. The lower cap r15 also is provided with a channel 29 extending axially through the cap through which the heat resisting liner may extend.

The upper cap 15 is formed to provide a threaded socket 31 extending inwardly and centrally of the bottom oi the socket 21 whereby to engage and support the upper end of the heat resisting liner. The upper cap 15 is also provided with an upwardly extending cylindrical portion 33 provided with screw threads 35. A channel v is formed through the portion 33 extendingfrom the bottom of the .threaded socket 31 upwardly through the'portion 33,y the upper end of the channel being restricted to provide a relatively narrow opening 39 through the top of the portion 33, the channel below this narrow opening being substantially large whereby to provide an explosion chamber 37 within the cap 15. cap 41 is provided to engage the threaded portion 35 ot' the upwardly extending portion 33 to seal the explosion chamber 37 at its opening 39 and to secure the upper end of the fuse wire to the upper cap The heat resisting liner comprises a relatively elongated outer tube 43 which may be formed of any suitable insulating material having relatively tough resilient characteristics and an inner heat and lire resisting lining 51 formed to the inner surfaces otl the tube 43. The tube 43 is threaded at its upper end 45 for engagement in the threaded socket 31 of the upper cap member 15 and is similarly threaded at its lower end 47 for engagement with a retaining cap 65. The lining 51 is arranged to extend throughout the length of the tube 49 and is curled over the upper end of the tube adjacent the explosion chamber 37, the cap 15 being provided with an annular groove 61 to accommodate the overlapping end of the lining 51. Although mayY employ various heat resisting materials for the liner 51, I prefer to use lavaalthough 'the same is somewhat brittle, because it can be accurately machined to size by turning in a suitable lathe. This enables me to form the fire resisting lining 51 so that it may be accurately fitted` into the bore 49 of the tube 43. By accurately fitting the lining51 into the tube 43, the same is supported lirmly by a closely iitted enclosing sheath, thus reducing breakage of the liner to a minimum. As a :further improvement, l prefer to form the lining 51 in sections 53. This is advantageous for the reason that a lining formed in short lengths is less likely to crack in service due' to the extreme heat to which the lining is subjected and for the additionalreason that the assembly of the lining in the tube 43 is facilitated when the lining is provided in short lengths, it

being readily appreciated that all refractory materials are somewhat brittle and that the handling of relatively elongated tubes of thin, brittle material is a delicate operation,- whereas the handling of short tubes of the same thickness is not fraught with the dan* ger of breakage. In order to seal the space between adjacent lengths of the sections 53 of the lining, I prefer to insert a thin Viilm of heat resisting cement 57 between the abutting ends of adjacent lining sections. I may also form the sections 53 to provide lap joints at their abutting ends, as shown clearly in Figure 5 of the drawings, in which case the cement may be dispensed with or not as desired. The overlapping of the lining 5l at the upper end of the tube 43 may be accomplished by providing a flanged disc 55 having a neck adapted to cooperate with the upper end of the uppermost section 53. The length of the tube y43 and of the sections 53 is `adjusted so that when the sections are assembled in the tube, the lower end of the lower section extends slightly below the lower end of the lower threaded end 47 of the tube 43 as shown clearly at 63 in Figure 3 of the drawings. The retaining cap 65 which is provided with a central opening of diameter equal to that of the bore 59 of the lining 51, is threaded to the lower end 47 of the tube 43 and screwed up tightly thereon so that the segments 53 of the lining are assembled in compression, it being understood of course that the upper threaded end 45 of the tube 43 is screwed up tightly into the threaded socket 3l of the head l5. By thus assembling the lining 5l under compression, I improve the strength of the liner assembly.

Then the upper end of the liner is screwed into the socket 3l, the bore 59 of the lining will form a continuation of the chamber 37 extending downwardly through the tube 13, through the lower cap member 15 and terminating at the lower end Vof the tube 43 as shown in Figure 3 ofthe drawings. The fuse consists of a wire 69 which may be formed of any well-known or suitable fusible material suchvfor instance as aluminum, zinc or copper, either pure or alloyed with materials. The wire, at its upper end, is formed to provide an outwardly extending stop whereby when the fuse is introduced through the opening 39 in the upper cap l5, this outwardly extending stop will lie open the top of the portion 33, as shown in Figure 3 of the drawings. The stop may be conveniently formed by connecting the upper end of the wire 69 to a link shaped member of suitable flexible current 5 conducting material, such for instance as lead. This link shaped member comprises a pair of discs joined by an integral connecting strip. One of the discs is provided with a perforation 73. The upper end of the fuse wire is inserted through the perforation 73 and is arranged to form a coil above the perforated disc which extends substantially at right angles to the shank or body portion of the lwire 69 which extends below theperforated disc. The integra-l interconnecting portion of the link 75 vis then bent and the unperforated disc portion is folded over above the coil 7l so that the coil is sandwiched be- `tween the perforated and unperforated por- This provides a simple tions of the link 75. means for securing the upper end of the fuse wire 69 to the cap member l5. The lower end of the fuse wire G9 is or may be braided or otherwise coiled with a second length of fuse wire 77 commencing at a point substantially below the coil 7l and extending throughout the remainder of the fuse wire. This is to insure that the rupture of the fuse wire occurs in the upper portions of the fuse, that is to say substantially in the explosion chamber 37 when the fuse is arranged in position in the fuse holder.

The fuse is arranged in the fuse holderby removing the cap 4l, inserting the braided' lower end of the fuse wire through the opening 39 and passing the same downwardly through the explosionk chamber 37 and tube 43 until the link member 75 engages the top of the portionv 33. The cap 4l is then threaded to the portion 33 to secure the upper end of the fuse wire firmly to the portion 33 and to seal the opening 39 so that the force of the explosion caused wire and the consequent creation of an arc in the explosion chamber may be directed downwardly through the tube 43. The fuse wire 69 is suiiiciently long to extend substantially below the lower end of the tube 43. The free braided end of the fuse wire G9 is finally secured to the boss 23 by means of the thumb screw 27 so as to electrically connect the upper and lower cap members l5 through the lining.

From the foregoing description it will be obvious that the fuse assembly of my invention will not deteriorate under overload conditions no matter how long such conditions may prevail. The channel through which the fuse 69 extends is lined with lava which fuses at around 2500 degrees centigrade. This lava channel is f-ormedas a thin walled cylf inder which is backedup and strengthened by a relatively tough, resilient material so that the chances of breaking the lava tube are reduced to a minimum. As a refinement I have also shown how to form the lava tube in short relatively strong sections wherebyfracturesl of the lava may be avoided. I have also shown how to assemble the lava lining in compression to thereby further strengthen the assembly.l The fuse housingjthus provided sus by the burning of the fuse i has the dual advantage of strength and dura bility in service. The housing will not char since lava is a true refractory material, that is to say, does not carbonize but rather fuses when heated above 2500 degrees centigrade.

Itis thought that the invention and numerous of itsattendant advantages will be understood from the foregoing description and it Vis apparent that numerous cianges may be made in the form, construction and arrangement of the numerous parts without departing from the spirit and scope of the invention or sacrificing any of its manifest advantages, the form herein described being a preferred embodiment for purposes of illus-1 tration. Y

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An electric fuse comprising a fuse holder and an elongated liner comprising a plurality of cylindrical tubes of lava supported in end to end relationship within the fuse holder.

2. An electric fuse comprising a fuse holder and an elongated liner comprising a plurality of cylindrical tubes of refractory material supported in end to end relationship and secured under compression within the fuse holder.

3. An electric fuse comprising a fuse holder and an elongated liner comprising` a plurality of cylindrical tubes of lava supported in end to end relationship and detachably mounted within the holder to form a channel therein lined with a refractory material.

il. An electric fuse comprising a frame, an elongated fuse holder arranged in the frame and comprising an insulating tube mounted in the frame and a refractory lining of lava forming a channel in the tube.

5. An electric fuse comprising a fuse holder forming a support frame, an elongated liner detachably arranged in the support frame and comprising an insulating tube and a re-4 movable refractory lining forming a channel in the tube through which a fuse may entend, said liningbeing formed as a plurality of sectons whereby to reduce the chances of frac turing the lining.

6. An electric fuse comprisinga support, means in said support providing spaced terminals to Which a fuse may be connected to extend therebetween and a fuse housing detachably mounted in the support around the fuse, said housing comprising an outer tube of insulating material and a removable inner lining of refractory material. extending from end to end of the housing whereby the tube insulates the terminals and the liner protects the tube from carbonization during service.

7 An electric fuse comprising a housing and means Within the housing forming a lava Y lined channel.

8. An electric fuse comprising a. housing and means Within the housing forming a channel lined withilava, said lava being arranged in tubes mounted in end to end relation whereby to provide a continuous chan nel. Y

9. A. fuse support comprising a housing, an elongated liner comprising a plurality of cylindrical tubes of lava and means for supporting the tubes in end to end relationship `within the fuse holder.

10. A fuse support comprising a housing, an elongated liner comprising a plurality of lava tubes forming a channel in the housing and a sheath comprising a tube enclosing the lava tubes and supporting them in end to end relationship. v

11. A fuse support comprising a housing, means in said housing providing insulated terminals to which a fuse may be attached to extend through the housing and a refractory liner detachably arranged within the housing around the fuse, said liner comprising an outer tube of insulating material and an inner lining of lava whereby the tube insulates the terminals and the liner protects the tube from carbonization during service.

12. ln combination, a fuse and a fuse holder comprising a housing and an elongated liner comprising aplurality of cylindrical tubes of refractory material supported in end to end relationship and detachably mounted within the holder to form a channel therein lined with a refractory material and means to secure the tubes in place under slight longitudinal compression.

`i3. In combination, a Afuse and av fuse holder comprising a housing, an elongated liner arranged in the housing and comprising an insulating tube mounted in the housing, a refractory lining comprising a plurality of abutting sections supported in the tube and means for securing the sections in place in the tube.

14. ln combination, a fuse and a fuse holder comprising a housing, an elongated liner detachably arranged in the housing and comprising an insulating tube mounted in the housing, a r fractory lining'comprising a plurality of tubular sections supported in end to end relationship in said tube and means for clamping the sections in place therein.

l5. in combination, a fuse and a fuse holder comprising a housing and means within the housing foming a channel lined with larva,l said' fuse extending through said channel.

1G. ln combination, a fuse and a fuse holder comprising a housing and means within the housing forming a channel lined with lava, said lava being arranged in tubes in end to end relation whereby to provide a continuous channel extending from Within the housing to a point outside of the housing, said fuse extending through said channel.

17. In combination, a fuse and a fuse holder comprising an outer tube of insulating material and an inner lining comprising a plurality of tubular sections of refractory material arranged in abuttingend to end relationship snugly within the tube and secured therein under longitudinal compression.

18. A fuse holder comprising a chambered member forming a terminal, said member having an opening,.a spaced terminal and a sleeve securing said terminals in spaced relationship, a tubular member detachably threaded at one end into said member and extending outwardly through said sleeve, said tubular member having a remote end extending beyond said spaced terminal, a fuse link extending in said tubular member, means to connect the link at one end to said chambered member and at the other end to the spaced terminal exter ally of the tubular member.

19. A fuse holder comprising a chambered member forming a terminal, said member having an opening, a spacing tube secured to and extending outwardly of said member, a terminal carried by said tube in spaced relation with the chambered member, a tubular member threaded at one end into the opening of said chamber member and extending outwardly through the spacing tube, a refractory lining in said tubular member, said lining abutting at one end of the tubular member against the chambered member, said tubular member having a remote end extending beyond a spaced terminal carried by the spacing tube and means to connect a fuse link, extending in said tubular member, at one end to said chambered member and at its other end to said spaced terminal.

20. A fuse holder comprising a chambered member forming a terminal, said member having an opening, a spacing tube secured to and extending outwardly of said member, a terminal carried by said tube in spaced relation with the chambered member, a tubular member mounted at one end in the opening of said chamber member and extending' outwardly through the spacing tube, said tubular member having' a remote end extending beyond a spaced terminal carried by the spacing tube, a refractory liner fitted snugly into the bore of the tubular member and abutting at vone end against ashoulder formed in the opening of the chambered member and means to secure the refractory liner in the tubular member under longitudinal compression, said terminals having means formed and arranged therein to connect a fuse link in the assembly in position to extend through the tubular member from the chambered member to the spaced terminal. i

2l. A fuse holder comprising a chambered member forming a terminal, said member having an opening, a spacing tube secured to and extending outwardly of said member, a terminal carried by said tube in spaced relaterminal secured to said tion with the chambered member, a tubular member mounted at one end in the'opening of said chamber member and extending' outwardly through the spacing tube, said tubularmember having' a remote end extending beyond a spaced terminal carried by the spacing tube, a refractory liner fitted snugly into the bore of the tubular member and abutting at one end against a shoulder formed in the opening of the chambered member and clamping means at the remote end of the tubular member for securing the liner in place in the tubular member under longitudinal compression, said terminals having means for securing a fuse link thereto.

22. A fuse holder comprising a chambered member forming a terminal, said member having an opening, a spacing tube secured `to and extending outwardly of said member, a terminal carried by said tube in spaced relation with the chambered member, a tubular member mounted at one end in the opening of said chamber member and extending outwardly through the spacing tube, said tubular member having a remote end extending beyond a spaced terminal carried by the spacing tube, a refractory liner itted snugly into the bore of the tubular member and abutting at one end against a shoulder formed in the opening of the chambered member, a cap having a portion engaging the other end of the liner and threadingly secured on the project-ing end of the tubular member for securing the liner in the tubular member under longitudinal compression and means for securing a fuse link, extending through said liner in said tubular member, to said spaced terminals.

23. A fuse holder comprising a socketed member forming a terminal, a glass tube extending outwardly of said terminal, a second glass tube in spaced relationship with respect to the iirst mentioned terminal, a tubular member of insulating material detachably connected to said terminal and extending outwardly of said terminal within said glass tube, said tubular member having a free end extending beyond said second terminal, a fire resistant liner in said tubular member, means to secure the liner in the tubular member under longitudinal compression, a fuse extending in said tubular member, means to connect said fuse at one end to said rst named terminal, said fuse having a portion extending outwardly of the free end of the tubular member and means to secure the fuse to said second named terminal.

24. A fuse holder comprising a socketed member forming a terminal, a spaced terminal and a sleeve of insulated material securing said terminals in spaced relationship, a tubular member d-etachably threaded at one end into said `socketed member and extending outwardly thereof through said sleeve, said tubular member having a remote end extending beyond said spaced terminal, and adapted to receive a fuse link therein, means to electrically connect the fuse link to said soeketed member and means to connect the fuse link to the chambered member and to the spaced terminal externally of the tubular member.

VIn Witness whereof, I have hereunto sub- 10 scribed my name.

' CYRIL H. THOMAS. 

